DS has a birthmark on the base of his spine that looks a bit like a butterfly - perfectly symmetrical. Just FYI in case other babies have this - I asked the pediatrician about it, and she said it was a concern for spina bifida occulta. He also has a teeny dimple right inside the top of his bum cheeks, which is another indicator of it. We did ultrasounds & x-rays and fortunately he doesn't have it - just has all the indicators of it. But before then I had just thought it was a cute birthmark!